refactor: move preconditions resolvers to dedicated files

[favna]

This gives sapphiredev/plugins#491 a better solution without as much code duplication. The methods parseConstructorPreConditionsNsfw, parseConstructorPreConditionsRunIn, parseConstructorPreConditionsRequiredClientPermissions, parseConstructorPreConditionsRequiredUserPermissions, and parseConstructorPreConditionsCooldown in the Command class are kept because otherwise, this would be a breaking change. I am still unsure if we want to deprecate those methods and remove them in a future major, then call the resolvers directly from parseConstructorPreConditions or not.